This invention relates to dental prophylaxis angles, and in particular to a dental prophylaxis angle which provides a long-lasting positive seal with a dental tool.
Dental prophylaxis angles (prophy angles) include a body part which carries a drive gear for attachment to a Doriot type handpiece and a head which carries a driven gear in engagement with the drive gear. A dental tool such as a prophy cup is carded by the driven gear. In one popular style of prophy angle, the driven gear includes an internally threaded bur tube, and the dental tool includes a threaded shank which screws into the bur tube. The bur tube extends into a cap which closes the head of the angle.
Some present angles, such as the angle sold under the name TS2 by Young Dental of Earth City, Mo., create a seal between the cap of the metal angle and the prophy cup which is secured to the angle. The TS2 angle provides a knife edge in the cap which cuts into a bottom edge of the cup to create a seal with the cup. One particularly effective manner of forming the seal with a specially designed dental tool is described my U.S. Pat. No. 5,484,284, which is incorporated herein by reference. A prophy cup in accordance with that application has been on sale for more than a year.
The knife edge on the cap of the TS2 angle is sufficiently delicate that it can be bent or chipped if the angle is accidentally dropped or bumped against a hard, sharp surface. When the knife edge is bent or chipped, the angle cap may not form a tight seal with the prophy cup. Debris, such as grit, saliva, etc., therefore may find its way into the inner workings of the angle. This can shorten the useable life of the angle.